I know what a hot wire foam cutter is, but I was interested in his exact setup.

I just used 3/4" PVC for the arm, chromium wire (found at a hobby shop) a single pole dimmer switch (on high the wire is way too hot) and a 25.2v 2a transformer from radio shack. The wood I had left over from another project. I can put more about my build with some pictures later if you are interested.

I also used a foam knife to make the initial cut to get the wire through.